Non concentric discharge table for rotary hearth calciner

ABSTRACT

The center of the discharge table normally used with rotary hearth calciners is moved away from the center line of the rotary hearth so that the coke moves out from under the soaking pit, giving greater access and ease of installation for rabbles which plow the coke to the edge of the discharge table.

'oct'z, 1973 i United States Patent" 1-19-11 Allred 404 VV V HHH H220440024 22 22 [54] NON CONCENTRIC DISCHARGE TABLE 3,064,960 11/1962Beckenbach...................... FOR ROTARY "EARTH CALCINER 1,429,9259/1922 Candlot 1,878,581 9/1932 Ad-Der-Halden [75] Inventor: Victor D.Allred, Llttleton, Colo. 3 53 592 10 1970 scharbrough e1 3,433,7133/1969 [73] Ass'gnee' g'gf' 1,376,567 5 1921 Nielsen et [22] Filed: 71970 Primary Examiner-Norman Yudkoff [21] Appl. No.: 89,321 AssistantExaminerDavid Edwards Attorney-Joseph C. Herring, Richard C. Willson,Jr. and Jack L. Hummel 202/262, 263/26, 214/35 [51] Int.

Cl0b 7/00 202/102, 103, 104,

202 i56: f5 2' 26'3" 0 99 The center of the discharge table normallyused with 263/26, 29, 44; 201/39 34; 214,17 D, 17 C rotary hearthcalciners is moved away from the center 35 R, 37 18 v line of the rotaryhearth so that the coke moves out from under the soaking pit, givinggreater access and [58] Field gile arch....

[56] References Cited ease of installation for rabbles which plow thecoke to the ed e of the discharge table UNITED STATES PATENTS g2,676,006 4/1954 Martin 263/26 6 Claims, 5 Drawing Figures PATENTED OCT2 I973 INVENTOR VICTOR D. ALLRED ATmRA/EY WITNESS PAIENTEBUBT 23.783.013

sum 3 [IF 3 WITNESS INVENTOR.

VICTOR D. ALLRED ATTORNEY NON CONCENTRIC DISCHARGE TABLE FOR ROTARYHEARTH CALCINER CROSS REFERENCES TO RELATED APPLICATIONS A variety ofpending and issued patent applications have taught rotary hearthfurnaces. These include U.S. Pat. No. 3,448,0l2; U.S. Pat. No.3,470,078, and U.S. Pat. No. 3,475,286 and U.S. Pat. applications Ser.No. 866,790 filed Oct. 6, I969, now U.S. Pat. No. 3,652,426, Ser. No.888,698 filed December 29, I969, Ser. No. 887,450 filed Dec. 22, 1969,now U.S. Pat. No. 3,612,497, Ser. No. 887,449 filed Dec. 22, 1969, nowU.S. Pat. No. 3,594,287.

A number of these patents teach the use of concentric discharge tablesonto which calcined coke or other material falls from the rotary hearthof the furnace. Such discharge tables are centered under the centeroutlet of the rotary hearth and plow means sweep the material from thecenter to the outer edge of the rotary discharge table. However, in allcases, the rotary discharge tables taught have been concentric with therotary hearth and have therefore not obtained the advantages of thepresent invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The presentinvention relates to thermolytic distillation processes, generallyclassified in Class 201, subclasses 33-34 of the United States PatentOffice.

2. Description of the Prior Art A variety of prior art patents havetaught discharge tables rotating beneath the soaking pit of a rotaryhearth furnace, but in each instance the discharge table has beenlocated so as to rotate about the same axis as the rotary hearth.Therefore, none of the prior art has apparently taught thenon-concentric relationship between rotary hearth and discharge tableand the attendant advantages as enjoyed by the present invention.Patents showing concentric rotary hearth and discharge tableinstallations include U.S. Pat. No. 3,470,068 and U.S. Pat. No.3,475,286 to J.L.I(emmerer, et al. and also U.S. Pat. No. 3,448,012 tothe inventor of the present invention.

SUMMARY General Statement of the Invention The invention is used inrotary hearth furnaces which have a delivery point at which materialsdelivered onto the rotary hearth and an outlet point at which materialleaves the hearth, and are generally provided with means for movingmaterial across the hearth from the delivery point to the outlet point,e.g., plows or rabbles. According to the present invention, thedischarge table is located so as to rotate about a different verticalaxis from the axis of rotation of the rotary hearth. That is, thedischarge table is non-concentric with the rotary hearth. By shiftingthe axis of the discharge table away from that of the rotary hearth, inrotary hearth installations having center discharges (soaking-pits), thecenter portion of the discharge table can be removed from the center ofthe soaking pit of the rotary hearth. The soaking pit discharge thenbecomes a true feed chute to the discharge table in similar manner tothat which the rotary hearth is fed. Installation of the rabbles to movethe calcined coke across the discharge table is thus greatly simplified.This invention has its greatest utility when using the discharge tableas a coke cooler.

The discharge table can be utilized as a cooler, either by the naturalconvection of air moving across the unradiated coke lying on thisportion of the discharge table, or by supplying fluids, e.g., waterspray or air circulating across the bed of cooling coke on the dischargetable or using a perforate discharge table with fluids moving throughthe bed of cooling coke.

Utility of the Invention The present invention is useful for theproduction of calcined coke which is used principally for themanufacture of electrodes for aluminum production and otherelectro-chemical processes. The invention has the advantages that thecoke is caused to move out from under the soaking pit in conventionalrotary hearth furnaces having center soaking pit-type outlets. Rabblesmay then be readily installed to move the coke across the dischargetable to a point where the coke falls from the edge of the table. Suchrabbles provide greater ease of access and installation than those whichare located on discharge tables concentric and directly beneath thesoaking pit.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a schematic view of a rotaryhearth having a discharge table located non-concentrically with thehearth. For ease of illustration the rabbles are omitted from thedischarge table assembly of FIG. 1.

FIG. 2 is a schematic plan view of the discharge table shown in FIG. 1showing schematically the rabbles, water spray, and steam manifold allsuspended above the discharge table.

FIG. 3 is a schematic ,view showing the non, concentric discharge tableof the present invention in use in conjunction with a rotary hearthhaving a discharge at the periphery rather than at the center. Such arotary hearth is described more: fully in U.S. Pat. application Ser. No.887,450 filed Dec. 22, 1969 by the inventor of the present invention.

FIG. 4 is a schematic diagram showing the use of a shielded annulardischarge table having cooling sprays and a single blade means forremoving cooled material from the discharge table after approximately asingle revolution.

FIG. 5 is a schematic plan view of the apparatus of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Apparatus Referring to FIG, 1,the rotary hearth is constructed and operates just as described in U.S.Pat. No. 3,475,286 with raw coke being placed on the hearth l0 andbeingmoved across by the action ofa series of rabbles, two of which are shownas 11, until it falls into a soaking pit l2. Coke from the soaking pitI2 falls orito the upper surface of discharge table 13 which rotatesabout an axis 14 which is offset from axis 15 of the rotary hearthfurnace. A water seal 16 seals a shroud 17 in gas-tight contact with theoutside of the soaking pit.

Referring to FIG. 2 (the plan view of the discharge table shown in FIG.1), water sprays 18 consisting of pipes having downward directed nozzlesspaced at intervals along their length, are suspended horizontally abovethe table extending in approximately radial di' rections. A series ofrabbles which are water cooled in the manner described in theaforementioned U.S. Pat. No. 3,475,286 distribute the calcined coke onthe surface of the discharge table 13 into a series of spiral furrows,moving the coke progressively outward until it is discharged bycontacting blade 21 of discharge chute 22. A steam manifold 23 isconnected to a blower (not shown) and to a dust collector (also notshown). The manifold is composed of a channel closed at one end with theopen portion facing downward. A flow of air through the open end of thechannel 24 causes steam rising from the coke to be pulled into theblower and dust collector arrangement, recovering some coke fines andreducing release of water vapor in the vicinity of the discharge table.

Operation Referring to FIG. 1, coke, deposited at the outer edge of therotary hearth is plowed from one furrow to the next, gradually movingfrom the deposit point toward the two rabbles 11 shown in FIG. 1. Thefirst of these contacts the coke, forming a furrow lying substantiallybetween the two plows shown in FIG. 1. After an additional revolutionthe innermost plow strikes the coke causing it to slide down theslightly slanting surface of the soaking pit inlet 26, through thesoaking pit proper, 12 onto the upper surface 13 of the discharge table.

The coke is formed into a furrow by the innermost of the discharge tableplows 20. After one revolution the coke is transferred to the next outerfurrow by the action of the plow which is second from the center of thedischarge table. During the next revolution the coke is subjectedtowater sprays which cool primarily the exposed surface of the coke. Thecoke then encounters the third plow from the center which, like all ofthe plows, turns the coke bed over, exposing a new surface. This newsurface is then cooled by contact with the water sprays during the nextrevolution. The next outer discharge table plow exposes still anothersurface which is cooled by water sprays and this process continues untilthe coke is discharged from the table by the action of plow 21 whichtransfers the coke into discharge chute 22 which delivers it toadditional cooling facilities, e.g., water cooled rotating shelves oraircooled open vibrating tables or chutes. Alternatively, the coke canbe transferred directly to conveyors which deliver it to a storagelocation provided that the temperature of the coke leaving the dischargetable has been reduced sufficiently to permit the coke to be storedwithout further cooling.

The steam generated by contact of the coke with water fills shroud l7and is withdrawn through steam manifold 23 which leads to dustcollection apparatus and the suction of a blower (both not shown),mentioned above.

It will be noted that the coke has at no time suffered any violentagitation which would cause breakage of the relatively friable cokeparticles, increasing the percentage of the coke which is in the form ofgenerally undesirable fine particles. This gentle treatment of the cokeby the process of the present invention is in sharp contrast to thevibrating conveyors and tumbling type drum coolers which are frequentlyutilized to move coke from the calciner and to cool it. Since thesoaking pit will generally be operated approximately full of coke, therewill be no severe drip from the hearth surface to the discharge table.Instead, the coke detained in the soaking pit will gradually movedownward as coke is removed from the bottom of the soaking pit by theaction of the rotating discharge table.

Modifications of the Invention It should be understood that theinvention is capable of a variety of modifications and variations whichwill be made apparent to those skilled in the art by a reading of thespecification and which are to be included within the spirit of theclaims appended hereto. Some of these modifications are mentioned below.

The material being heat treated can be petroleum coke, including bothdelayed and fluid petroleum coke, coal, pellets or briquets containingbituminous coking coal or other carbonaceous materials together with abinder, limestone, dolomite, cement rock, carbonates from which thecorresponding metal oxides are to be reclaimed, sulfates or chloridesfor decomposition, oil shale for recovery of oil, and many othermaterials to be subjected to heat treatment.

The temperature in the rotary hearth is not narrowly critical, but incalcining petroleum cokes will generally be in the range of from aboutl,500 to 3,000F., more preferably 1,800 to 2,700F., and most preferably2200 to 2,500F., as measured at the bed of calcining material.Temperatures for calcining coal will be in the range of from 1,000 to2,500, more preferably 1,200 to 2200, and most preferably 1,800 to2,100F., with most coals. Temperatures for calcining other materialswill be selected in accordance with the well-known techniques for suchcalcining.

The fluids used to cool the material on the discharge table willgenerally be water or air, but may be nitrogen or other non-reactivegases or steam or any other fluid capable of removing heat from thematerial on the discharge table without entering into undesirablechemical reactions with the material. The quantity of cooling fluids tobe utilized will, of course, vary with the temperature and heat capacityof the material being deposi'ted on the surface of the discharge tableand the degree of cooling required.

FIG. 3 shows a discharge table of the general type shown in FIGS. 1 and2, but used in conjunction with a peripheral-discharge rotary hearthfurnace of the type described in copending U.S. Pat. application Ser.No. 887,450 filed Dec. 29, 1969. The feed enters through a conventionalfeed chute 40 (shown schematically) near the center of the rotatinghearth 41 and is arranged in furrows which are gradually moved from thecenter toward the periphery of the rotary hearth by means of rabbles 42through 45. Rabble 45 dislodges the calcined coke from the hearth 41 andsends it through a feed chute 46 into a small soaking pit 47. Thissoaking pit operates essentially full of coke and permits the varioussizes of coke particles to come to a uniform temperature prior tocooling. This final temperature reachedby the coke is especiallyimportant in maintaining high quality such as low coefficient'of thermalexpansion, a property particularly desired in cokes to be used forelectrodes. The discharge table 48 is equipped with rabbles, watersprays, a shroud and steam manifold (all not shown) of the type shown inFIGS. l-3.

The configuration of the discharge table may be varied. For example, asshown in FIG. 4, the table 30 and the shroud 31 are annular with asingle blade 32 (shown in FIG. 5) removing the coke from the table afterone revolution of the table. The tunnel" or doughnut configuration isparticularly useful for moving the calcined coke in a horizontal mannerout from under the hearth. lt also generally allows a greater area forcooling the coke since the size will not be limited by the supportingmembers (not shown) for the rotary hearth. Conventional dust collectingapparatus 35 can be connected to the shroud to withdraw steam andrecover fine particles of carbon. The water seal 33, soaking pit 12,rotary hearth l0, and rabbles 11 and the other components of the rotaryhearth furnace can be as shown in FIGS. 1 and 2. Operation is, ingeneral, similar to that described above in connection with FIGS. 1 and2. A vibratory conveyor 34 can serve to remove the material from thecooler discharge.

What is claimed is:

1. In a rotary hearth furnace having a delivery point at which materialis delivered to said rotating hearth and a central outlet point at whichmaterial leaves said rotating hearth and means for moving materialacross said hearth from said delivery point to said outlet point, theimprovement comprising a discharge table located to receive material asit leaves said rotating hearth at said outlet point, said dischargetable itself comprising a table rotating about a fixed axis and having adeposit point for receiving material from said rotary hearth and anoutlet point for discharging material from said discharge table andmeans for moving materials from said deposit piont to said outlet pointon said discharge table, said fixed axis of said discharge table beingoffset away from the axis of said rotating rotary hearth,

wherein the delivery point is located substantially on the periphery ofsaid rotary hearth and whereinrthe outlet point is located substantiallyat the center of said rotary hearth, and wherein at least one plowdepends above said discharge table and wherein the material is movedacross said discharge table from said delivery point to said outletpoint by means of said at least one plow moving relative to saiddischarge table.

2. Apparatus according to claim 1 wherein the delivery point is locatedsubstantially on the periphery of said rotary hearth and wherein theoutlet point is located substantially at the center of said rotaryhearth.

3. Apparatus according to claim 1 wherein the delivery point is locatedsubstantially at the center of said discharge table and wherein theoutlet point is located substantially at the periphery of said dischargetable.

4. Apparatus according to claim 2 wherein the delivery point is locatedsubstantially at the center of said discharge table and wherein theoutlet point is located substantially at the periphery of said dischargetable.

5. In a rotary hearth furnace of claim 1, the further improvementcomprising cooling means located above said discharge table fordistributing fluids downward onto said materials on said dischargetable.

6. Apparatus according to claim 6 wherein water sprays are providedabove said discharge table for cooling material on said discharge tableby directing water downward to contact said material on said dischargetable.

UNITED STATES PATENT OFFICE CERTIFICATE or eoRREcTmN Patent No 3,763,013 Dated 10/2/7 Inventor(s) VICTOR D. ALLRED It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Col. 3, line 66: Delete "drip" and insert therefor -drop.

Claim 6, line 26: Delete "according to Claim 6" and insert according toClaim 5.

Signed and Scaled this Sixth Day of September 1977 [SEAL] Attest:

RUTH C. MASON LUTRELLE F. PARKER Attesting Officer Acting Commissionerof Patents and Trademarks

2. Apparatus according to claim 1 wherein the delivery point is locatedsubstantially on the periphery of said rotary hearth and wherein theoutlet point is located substantially at the center of said rotaryhearth.
 3. Apparatus according to claim 1 wherein the delivery point islocated substantially at the center of said discharge table and whereinthe outlet point is located substantially at the periphery of saiddischarge table.
 4. Apparatus according to claim 2 wherein the deliverypoint is located substantially at the center of said discharge table andwherein the outlet point is located substantially at the periphery ofsaid discharge table.
 5. In a rotary hearth furnace of claim 1, thefurther improvement comprising cooling means located above saiddischarge table for distributing fluids downward onto said materials onsaid discharge table.
 6. Apparatus according to claim 6 wherein watersprays are provided above said discharge table for cooling material onsaid discharge table by directing water downward to contact saidmaterial on said discharge table.